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Re: SSD + RAID

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From:	Bruce Momjian
Subject:	Re: SSD + RAID
Date:	22 February 2010 , 13:40:07
Msg-id:	201002221439.o1MEdth13439@momjian.us (view: Whole thread, Raw)
In response to:	Re: SSD + RAID (Ron Mayer)
List:	pgsql-performance

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SSD + RAID (Laszlo Nagy, 13 November 2009, 11:46:34 )
Re: SSD + RAID (Karl Denninger, 13 November 2009, 12:04:28 )
Re: SSD + RAID (Laszlo Nagy, 13 November 2009, 12:59:16 )
Re: SSD + RAID (Axel Rau, 20 November 2009, 10:25:34 )
Re: SSD + RAID (Richard Neill, 20 November 2009, 18:00:09 )
Re: SSD + RAID (Greg Smith, 20 November 2009, 23:27:57 )
Re: SSD + RAID (Merlin Moncure, 21 November 2009, 13:25:14 )
Re: SSD + RAID (Marcos Ortiz Valmaseda, 13 November 2009, 13:07:41 )
Re: SSD + RAID (Scott Marlowe, 13 November 2009, 13:49:21 )
Re: SSD + RAID (Merlin Moncure, 13 November 2009, 14:29:58 )
Re: SSD + RAID (Scott Carey, 13 November 2009, 16:22:57 )
Re: SSD + RAID (Merlin Moncure, 13 November 2009, 17:31:43 )
Re: SSD + RAID (Heikki Linnakangas, 13 November 2009, 14:36:46 )
Re: SSD + RAID (Merlin Moncure, 13 November 2009, 14:59:20 )
Re: SSD + RAID (Heikki Linnakangas, 14 November 2009, 10:17:31 )
Re: SSD + RAID (Merlin Moncure, 14 November 2009, 12:05:39 )
Re: SSD + RAID (Heikki Linnakangas, 14 November 2009, 12:47:03 )
Re: SSD + RAID (Merlin Moncure, 14 November 2009, 20:30:49 )
Re: SSD + RAID (Laszlo Nagy, 14 November 2009, 17:39:56 )
Re: SSD + RAID (Robert Haas, 14 November 2009, 19:03:46 )
Re: SSD + RAID (Laszlo Nagy, 15 November 2009, 04:40:06 )
Re: SSD + RAID (Greg Smith, 13 November 2009, 16:21:52 )
Re: SSD + RAID (Karl Denninger, 13 November 2009, 16:37:09 )
Re: SSD + RAID (Greg Smith, 13 November 2009, 17:08:04 )
Re: SSD + RAID (Karl Denninger, 13 November 2009, 17:22:57 )
Re: SSD + RAID (Scott Carey, 19 November 2009, 03:07:24 )
Re: SSD + RAID (Tom Lane, 19 November 2009, 03:24:12 )
Re: SSD + RAID (Jeff Janes, 20 November 2009, 15:47:12 )
Re: SSD + RAID (Greg Smith, 19 November 2009, 13:44:56 )
Re: SSD + RAID (Karl Denninger, 19 November 2009, 13:46:50 )
Re: SSD + RAID (Brad Nicholson, 13 November 2009, 18:24:21 )
Re: SSD + RAID (Dave Crooke, 13 November 2009, 19:22:33 )
Re: SSD + RAID (Greg Smith, 13 November 2009, 20:06:50 )
Re: SSD + RAID (Merlin Moncure, 13 November 2009, 20:09:31 )
Re: SSD + RAID (Merlin Moncure, 17 November 2009, 15:36:35 )
Re: SSD + RAID (Brad Nicholson, 17 November 2009, 15:54:55 )
Re: SSD + RAID (Scott Marlowe, 17 November 2009, 16:04:31 )
Re: SSD + RAID (Peter Eisentraut, 17 November 2009, 16:30:28 )
Re: SSD + RAID (Greg Smith, 17 November 2009, 17:51:36 )
Re: SSD + RAID (Merlin Moncure, 17 November 2009, 18:19:50 )
Re: SSD + RAID (Greg Smith, 18 November 2009, 05:32:21 )
Re: SSD + RAID (, 18 November 2009, 05:59:10 )
Re: SSD + RAID (Scott Carey, 19 November 2009, 03:39:49 )
Re: SSD + RAID (Merlin Moncure, 19 November 2009, 16:01:36 )
Re: SSD + RAID (Scott Marlowe, 19 November 2009, 16:19:50 )
Re: SSD + RAID (Greg Smith, 19 November 2009, 20:11:41 )
Re: SSD + RAID (Merlin Moncure, 19 November 2009, 20:39:55 )
Re: SSD + RAID (Scott Marlowe, 19 November 2009, 20:52:18 )
Re: SSD + RAID (Mark Mielke, 17 November 2009, 19:43:38 )
Re: SSD + RAID (Scott Carey, 19 November 2009, 03:35:49 )
Re: SSD + RAID (Greg Smith, 19 November 2009, 13:49:27 )
Re: SSD + RAID (Bruce Momjian, 28 November 2009, 15:21:25 )
Re: SSD + RAID (Ron Mayer, 29 November 2009, 23:52:14 )
Re: SSD + RAID (Bruce Momjian, 30 November 2009, 02:10:03 )
Re: SSD + RAID (Greg Smith, 30 November 2009, 04:27:49 )
Re: SSD + RAID (Bruce Momjian, 30 November 2009, 11:09:01 )
Re: SSD + RAID (Ron Mayer, 30 November 2009, 15:32:46 )
Re: SSD + RAID (Bruce Momjian, 30 November 2009, 15:40:56 )
Re: SSD + RAID (Ron Mayer, 30 November 2009, 14:54:11 )
Re: SSD + RAID (Merlin Moncure, 13 November 2009, 17:57:40 )
Re: SSD + RAID (Matthew Wakeling, 08 December 2009, 13:22:40 )
Re: SSD + RAID (Bruce Momjian, 20 February 2010, 17:29:11 )
Re: SSD + RAID (Dan Langille, 20 February 2010, 22:16:49 )
Re: SSD + RAID (Bruce Momjian, 20 February 2010, 22:19:26 )
Re: SSD + RAID (Scott Carey, 21 February 2010, 08:35:55 )
Re: SSD + RAID (Bruce Momjian, 21 February 2010, 13:11:05 )
Re: SSD + RAID (Ron Mayer, 21 February 2010, 14:01:17 )
Re: SSD + RAID (Greg Smith, 22 February 2010, 04:39:23 )
Re: SSD + RAID (Arjen van der Meijden, 22 February 2010, 06:11:13 )
Re: SSD + RAID (Greg Smith, 23 February 2010, 00:05:05 )
Re: SSD + RAID (Mark Mielke, 23 February 2010, 00:11:42 )
Re: SSD + RAID (Greg Smith, 23 February 2010, 00:40:03 )
Re: SSD + RAID (Scott Marlowe, 23 February 2010, 01:21:53 )
Re: SSD + RAID (Scott Marlowe, 23 February 2010, 01:23:09 )
Re: SSD + RAID ("Pierre C", 23 February 2010, 10:51:02 )
Re: SSD + RAID (Nikolas Everett, 23 February 2010, 11:07:57 )
Re: SSD + RAID (Scott Carey, 23 February 2010, 17:38:08 )
Re: SSD + RAID (Bruce Momjian, 22 February 2010, 13:37:49 )
Re: SSD + RAID (Ron Mayer, 22 February 2010, 17:00:47 )
Re: SSD + RAID (Greg Smith, 23 February 2010, 00:15:24 )
Re: SSD + RAID (, 23 February 2010, 07:24:03 )
Re: SSD + RAID (, 23 February 2010, 19:05:11 )
Re: SSD + RAID (Aidan Van Dyk, 23 February 2010, 19:35:01 )
Re: SSD + RAID (, 23 February 2010, 20:24:07 )
Re: SSD + RAID (Mark Mielke, 23 February 2010, 20:32:33 )
Re: SSD + RAID (Dave Crooke, 24 February 2010, 07:32:54 )
Re: SSD + RAID (Bruce Momjian, 27 February 2010, 00:40:31 )
Re: SSD + RAID (Greg Smith, 27 February 2010, 18:38:43 )
Re: SSD + RAID (Bruce Momjian, 27 February 2010, 19:16:47 )
Re: SSD + RAID (Ron Mayer, 28 February 2010, 03:05:29 )
Re: SSD + RAID (Greg Smith, 28 February 2010, 04:07:00 )
Re: SSD + RAID (Bruce Momjian, 02 March 2010, 02:35:18 )
Re: SSD + RAID (Bruce Momjian, 02 March 2010, 02:34:11 )
Re: SSD + RAID (Greg Smith, 02 March 2010, 05:13:51 )
Re: SSD + RAID (Ron Mayer, 03 March 2010, 14:16:52 )
Re: SSD + RAID ("Pierre C", 02 March 2010, 07:38:56 )
Re: SSD + RAID (Bruce Momjian, 22 February 2010, 13:40:07 )
Re: SSD + RAID ("Fernando Hevia", 13 November 2009, 19:56:53 )
Re: SSD + RAID (Greg Smith, 13 November 2009, 20:10:34 )
Re: SSD + RAID ("Kenny Gorman", 13 November 2009, 20:36:12 )
Re: SSD + RAID (Kenny Gorman, 18 November 2009, 21:59:53 )
Re: SSD + RAID (Lists, 14 November 2009, 08:40:52 )
Re: SSD + RAID (Ivan Voras, 14 November 2009, 09:43:12 )
Re: SSD + RAID (Laszlo Nagy, 15 November 2009, 06:27:20 )
Re: SSD + RAID (Craig Ringer, 15 November 2009, 07:47:22 )
Re: SSD + RAID (Laszlo Nagy, 15 November 2009, 08:35:36 )
Re: SSD + RAID (Craig Ringer, 15 November 2009, 09:17:43 )
Re: SSD + RAID (Laszlo Nagy, 15 November 2009, 10:46:01 )
Re: SSD + RAID (Craig James, 15 November 2009, 19:25:11 )
Re: SSD + RAID (Heikki Linnakangas, 15 November 2009, 19:42:16 )
Re: SSD + RAID (Scott Carey, 19 November 2009, 03:23:14 )
Re: SSD + RAID (Craig Ringer, 19 November 2009, 11:30:15 )
Re: SSD + RAID (Anton Rommerskirchen, 19 November 2009, 17:10:30 )
Re: SSD + RAID (Brad Nicholson, 19 November 2009, 17:58:03 )
Re: SSD + RAID (Greg Smith, 19 November 2009, 20:04:57 )
Re: SSD + RAID (Matthew Wakeling, 20 November 2009, 10:55:14 )
Re: SSD + RAID (Scott Carey, 03 December 2009, 23:05:51 )

Ron Mayer wrote:
> Bruce Momjian wrote:
> > Agreed, thought I thought the problem was that SSDs lie about their
> > cache flush like SATA drives do, or is there something I am missing?
>
> There's exactly one case I can find[1] where this century's IDE
> drives lied more than any other drive with a cache:
>
>   Under 120GB Maxtor drives from late 2003 to early 2004.
>
> and it's apparently been worked around for years.
>
> Those drives claimed to support the "FLUSH_CACHE_EXT" feature (IDE
> command 0xEA), but did not support sending 48-bit commands which
> was needed to send the cache flushing command.
>
> And for that case a workaround for Linux was quickly identified by
> checking for *both* the support for 48-bit commands and support for the
> flush cache extension[2].
>
>
> Beyond those 2004 drive + 2003 kernel systems, I think most the rest
> of such reports have been various misfeatures in some of Linux's
> filesystems (like EXT3 that only wants to send drives cache-flushing
> commands when inode change[3]) and linux software raid misfeatures....
>
> ...and ISTM those would affect SSDs the same way they'd affect SATA drives.

I think the point is not that drives lie about their write-back and
write-through behavior, but rather that many SATA/IDE drives default to
write-back, and not write-through, and many administrators an file
systems are not aware of this behavior.

--
  Bruce Momjian  <>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com
  PG East:  http://www.enterprisedb.com/community/nav-pg-east-2010.do
  + If your life is a hard drive, Christ can be your backup. +

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